Belt tightener for grinding machines

ABSTRACT

The disclosure relates to a belt tightener for a grinding machine. A drive unit has a belt extending to the grinding wheel, and a power device has a lost-motion connection with the drive unit to retract the drive unit away from the grinding wheel to tension the belt. A latch holds the drive unit retracted. A cam carried by the power device is operative within the limits of the lost-motion connection to release the latch when the power device is reversed to thereby untension the belt.

United States Patent inventor Appl. No

Filed Patented Assignee Richard G. Hopkins Bennington Township, Shiawsssee County, Mich.

Dec. 2, 1969 Sept. 14, 1971 MWA Company Owasso, Mich.

BELT TIGHTENER FOR GRINDING MACHINES 11 Claims, 3 Drawing Figs.

U.S.Cl 51/35,

- 74/242.13 R int. Cl 1324b 7/02,

F16h 7/10 Field of Search 51/ 35, 135

BT; 74/242.l3A, 242.14 R

[56] References Cited UNITED STATES PATENTS 3,197,163 7/1965 Litosch 74/2 1213 X 3,451,170 6/1969 Reppenhagen 51/35 1,629,918 5/1927 Kastler 74/242.13 R

Primary ExaminerHarold D. Whitehead AnorneyWhittemore, Hulbert & Belknap ABSTRACT: The disclosure relates to a belt tightener for a grinding machine. A drive unit has a belt extending to the grinding wheel, and a power device has a lost-motion connection with the drive unit to retract the drive unit away from the grinding wheel to tension the belt. A latch holds the drive unit retracted. A cam carried by the power device is operative within the limits of the lost-motion connection to release the latch when the power device is reversed to thereby untension the belt,

SHEET 2 [IF 2 ATTOR NEYS BELT TIGHTENER FOR GRINDING MACHINES SUMMARY OF THE INVENTION One object of this invention is to provide an improved belt tightener for a grinding machine which includes means for holding the belt in tension and also for releasing the tension.

Another object is to provide a belt tightener which is an improvement on the belt tighteners shown in U.S. Pat. Nos. 3,451,170, 3,335,525, 2,845,751, 2,750,714 and 2,741,070.

Another object is to provide a grinding machine including a drive unit having a belt extending to the grinding wheel to rotate it, a power device for retracting the drive unit to tension the belt, latch means for holding the drive unit retracted and cam means for releasing the latch means to untension the belt.

Another object is to provide a lost-motion connection between the drive unit and the power device so that the cam means may be operative within the limits of the lost-motion connection.

Another object is to provide means for holding the latch in its operative position to retain the tension on the belt.

Another object is to provide a latch means for holding the power device retracted which is automatically rendered operative in response to retraction of the drive unit.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view of a grinding machine embodying my invention.

FIG. 2 isan enlarged fragmentary view with parts in elevation and parts in section of a portion of the structure shown in FIG. 1.

FIG. 3 is a detail view showing a modification of a portion of FIG. 2.

Referring now more particularly to the drawings and especially to FIGS. 1 and 2, the grinding machine is generally indicated at 9 and comprises a carriage 10 having wheels 12 and 14 supporting the carriage for movement along the parallel tracks 16 on the floor.

The machine also includes a saddle 22 mounted on the carriage 10 for movement at right angles to the path of the carriage. A grinding unit 24 is mounted on the saddle for vertical swinging movement about the axis of the horizontal pivot shaft 26. Shaft 26.is parallel to the carriage path.

Spaced, parallel rods are mounted on the carriage path. One such rod. is indicated at 28. The opposite ends of the rods are mounted'on rod supports 30 rigidly securedto the carriage platform at opposite sides of the saddle 22. The saddle has suitable bearing supports, not shown, through which the rods 28 extend and by which the saddle 22 is supported and guided for movement lengthwise of rods 28. The horizontal pivot shaft 26 for the grinding unit 24 is mounted on the saddle 22 by the support 27. Suitable power means such as a rack-andpinion-type drive or a fluid-operated piston-cylinder assembly may be provided to move the saddle back and forth as desired on the rods 28. A suitable drive 29 is provided for moving the carriage on tracks 16.

The grinding unit 24 includes a base 40, a boom 42 rigidly mounted on the base and projecting outwardly therefrom in the direction of saddle movement, a grinding head 44 mounted on the outer end of the boom, and a drive unit 46 mounted on the base 40. A fluid-operated piston-cylinder assembly 48 is-provided to pivot the grinding unit 24 about the axis of pivot shaft 26. The cylinder portion of the pistoncylinder 48 is pivoted at 49 to the bracket 50 on saddle 24 and the piston portion of the assembly 48 is pivoted at 52 to bracket 54 carried by grinding unit 24.

The grinding head 44 includes a frame 56 having a pivot shaft 58 upon which a grinding wheel G is mounted for rotation. A pulley 60 on shaft 58 is secured to thegrinding wheel G so that the pulley and grinding wheel-rotate as a unit.

The drive unit 46 includes a supporting-frame 62 which is mounted for sliding movement in ways 64 on the base 40. The

frame 62 may thus slide back and forth in a direction which is lengthwise of the boom 42, toward and away from the grinding wheel G. The drive unit 46 also includes a motor 66 mounted on the frame 62, and a gear reduction unit 68 mounted on frame 62 and driven by motor 66.-The gear reduction unit 68 has an output pulley 70, and an endless belt 72 extends around the two pulleys 60 and 70.

The piston'cylinder assembly 48 is used to lower the grinding wheel G into grinding contact with a workpiece and to raise the grinding wheel away from grinding'contact. In time the grinding wheel wears down and needs to be replaced. In order to replace the grinding wheel, the belt 42 has to be removed and to do this the normal tension on the belt required for proper operation has to be relieved so that it can be taken off the pulley 60. I

The means for tensioning and untensioning the belt 72 is best shown in FIG. 2. As there shown, a fluid-operated pistoncylinder assembly is provided,- the cylinder 82 of which is rigidly mounted on a bracket 84 bolted to the base 40 of the grinding unit 24. A piston, now shown, slidable within the cylinder 82 has a piston rod 86 extending from the cylinder. The entire piston-cylinder 80 including rod 86 extends parallel to the path of movement of the drive unit 46. A rod extension member 88 which is here shown in the form of a bolt, has a shank the end portion 90 of which is threaded into a socket 92 in the end of piston rod 86 and pinned in the socket by pin 94. A cam 96 having a through central passage is provided, the central passage including an enlarged portion 98 and a reduced portion 100 separated by a shoulder 102. The cam is mounted on the piston rod 86 and on the unthreaded portion of the shank of bolt 88, the rod 86 extending into the enlarged portion 98 of the through passage and the unthreaded shank of the bolt 88 extending through the reduced portion 100.'The bolt 88 has an enlarged collar 104 between its head 106 and its shank providing a shoulder 108 which bears against the end of the cam 96 and clamps the internal shoulder 102 of the cam against the end ofthe piston rod. The cam is of symmetrical form about its axis andhas the inclined annular frustoconical surface 110.

An adjusting screw 112 is provided on the frame 62 of drive justing screw 112 threads through the bushing nut. Screw 112 extends parallel to the path of movement of the drive unit 46 and parallel to the piston-cylinder assembly 80. The screw 112 has an integral nut 118 near its outer end provided with suitable flats so that the screw may-be adjusted by applyinga wrench or suitable tool to the nut 118.

An adapter 120 is provided having a cylindrical'portion 122. A cylindrical socket 124 is provided in the cylindrical portion 122 having an enlarged. threaded portion 126. anda reduced portion 128. The outer end of the adjusting screw 112' threads into the threaded portion 126 of the socket and is pinned thereto by a pin 130.

The adapter 120 has an enlarged circular head 132 at the outer end of the cylindrical portion 122 and there is an axial passage 134 through the head. The collar portion 104 of bolt 88 extends slidably through the passage 134, and the head 106 of the bolt is slidably disposed in the reduced portion 128 of the socket 124 in the adapter 120.

A locknut is threaded on the screw 112 and is'adapted to be threaded up tight against the end face of bushing nut 114 to lock the screw 112 in adjusted position.

The piston-cylinder assembly 80 is a reversible power device with suitable fluid lines leading to opposite ends so that the piston rod 86 may be moved in opposite directions. Obviously when the piston rod is moved to the right it will correspondingly move the drive unit 46 to the right throughits connection with the drive unit by means of screw I12 and adapter 120. There is lost motion in the connection between.

piston rod 86 and screw 112 in the amount of the distance between the head 106 of bolt 88 and the outer end of screw 112 within the socket 124 of adapter 120. Thus whenthe piston rod 86 is moved to the left, this movement may initially take place without a corresponding movement to the left of the drive unit 46 within the limits of the lost-motion connection.

A latch 150 is provided for locking the drive unit 46 in the retracted position shown in FIG. 2. The latch 150 is an elongated plate or bar which is pivoted at its inner end to the bracket 84 by pin 152. The outer end of the latch is formed with a nose 154 having a hook portion 155 which is adapted to engage the radially inner surface 156 on the head 132 of the adapter 120 to retain the drive unit 46 in the retracted position shown. In this retracted position the belt 72 is held under tension for normal grinding. A plunger 160 is mounted for vertical movement in a cylinder 162 secured to the bracket 84 above the latch 150. A coil spring 164 in the cylinder bears down upon the plunger 60 and the plunger bears down upon the latch 150 with a constant pressure to normally urge the latch to its operative position shown in FIG. 2.

The latch 150 has a lower projection 166 between its nose 155 and its pivot 152 formed with the beveled surfaces 168 and 170. Under normal operating conditions, the large portion of the cam 96 is in the recessed portion 172 of the latch between the projection 166 and the pivot 152.

As stated, the grinding machine is operated with the parts in the positions shown in FIGS. 1 and 2 in which the grinding unit 46 is latched in its retracted position by the latch 150. The plunger 160 will retain the latch in the position shown despite normal vibrations inherent in a grinding operation. When it is desired to replace a worn grinding wheel, the belt 72 has to be taken off pulley 60 and to accomplish this the belt tension must be relieved. In order to relieve belt tension the pistoncylinder assembly 80 is operated to move the piston rod 86 to the left. Initial leftward movement of the piston rod 86 will cause the cam surface 110 of cam 96 to engage the inclined surface 170 on the latch and cam the latch upward against the spring pressure of the plunger 160 to release the adapter 120 from the latch. This initial movement of the rod 86 takes place within the limits of the lost-motion connection, that is before the head 106 of bolt 88 comes in contact with the outer end of adjusting screw 112. The tension on the belt is thereupon released and continued movement of the piston rod 86 to the left will move the drive unit 46 to the left after the lost motion has been taken up.

After the grinding wheel has been replaced and the belt 72 put back on pulley 60, tension may again be applied to. the belt by reversing the power device 80 to move piston rod 86 to the right. The head 106 of bolt 104 will engage the bottom of the reduced-socket portion 128 of adapter 120 to move the adapter'and screw 112 and hence the drive unit 46 to the right. The nose portion of the latch 150 has an inclined outer surface 180 and there is a corresponding inclined surface 182 on the head 132 of the adapter so that the adapter head can obviously cam the latch 150 upward as it moves to the right past the nose of the latch 150. Likewise the annular cam surface 184 may engage the latch surface 168 and cam past it. When the drive unit has been retracted to the position shown in FIGS. 1 and 2, the latch 150 will be forced downward to its operative position by spring plunger 160 to lock the drive unit in retracted position. The fluid pressure in the cylinder 80 may be relieved. if a minor adjustment is desired in belt tension, the screw 112 may be rotated for this purpose and the nut 140 tightened against bushing nut 114 to maintain the adjustment.

FIG. 3 illustrates a modification in which a positive locking device 190 is provided for holding the latch down, in latching position with a positive action, in place of the springplunger 160. The device 190 includes a cam block 191 mounted on the bracket 84 above the latch and having a rotating cam 192 mounted for rotation on the cam block by a pin 193. The cam 192 has a flat surface 194 engageable with the upper surface of latch 150 in the position of the cam shown to positively hold the latch down in its operative position. The cam also has a relieved flat surface 195 spaced a lesser distance from the cam axis than the surface 194 so that when the cam is rotated to a position in which the relieved surface 195 overlies the latch, the latch may be manually disengaged from the adapter after first moving the adapter slightly to the right in FIGS. 1 and 2 by the operation of power device 80 to relieve the pressure of engagement on the latch. The cam is manually rotatable by the handle 196 from the position shown in which the cam surface 194 overlies the latch to a position in which the relieved surface 195 overlies the latch. The cam is shown in dotted lines with its handle 196 engaging stop 197 on cam block 191. Although the cam in the dotted position has swung past the position in which surface 195 is horizontal, obviously the cam is free to return to the latter position when the latch is cammed upwardly and released.

What I claim as my invention is:

1. A grinding machine comprising a grinding wheel, a drive unit having a belt extending to said grinding wheel to rotate the latter, a reversible power device having a lost-motion connection with said drive unit and operative when actuated in one direction to retract said drive unit away from said grinding wheel to a predetermined position tensioning said belt, latch means for holding said drive unit retracted in said predetermined position, and cam means carried by said power device and operative when said power device is actuated in the opposite direction to release said latch means and thereby untension said belt, said cam means effecting the release of said latch means within the limits of said lost-motion connection.

2. A grinding machine comprising a grinding wheel, a drive unit movable toward and away from said grinding wheel and having a belt extending to said grinding wheel to rotate the latter, a reversible power device having a reciprocable member, a lost-motion connection between said reciprocable member and said drive unit for retracting said drive unit away from said grinding wheel to a predetermined position tensioning said belt when said reciprocable member is moved in one direction by said power device, said lost-motion connection permitting initial movement of said reciprocable member in the opposite direction without corresponding movement of said drive unit, latch means for holding said drive unit retracted in said predetermined position, and cam means carried by said reciprocable member and operative during said initial movement of said reciprocable member in said opposite direction to release said latch means.

3. The grinding machine defined in claim 2, wherein said latch means comprises a pivoted latch having a hooked portion, said drive unit having a complementary member adapted to be engaged by the hooked portion of said latch to hold said drive unit retracted as aforesaid, said latch having a portion adapted to be engaged by said cam means during initial movement of said reciprocable member in said opposite direction to release said latch.

4. The grinding machine defined in claim 3, including means mounting said complementary member on said drive unit in selected positions of adjustment in the direction of movement of said drive unit.

5. The grinding machine defined in claim 3, including resilient means for holding said latch in its latching position.

6. The grinding machine defined in claim 3, including releasable means for positively locking said latch in its latching position.

7. The grinding machine defined in claim 2, wherein said latch means comprises a pivoted latch having a hooked end portion, said drive unit having a complementary member adapted to be engaged by the hooked portion of said latch to hold said drive unit retracted as aforesaid, said power device comprises a piston-cylinder assembly and said reciprocable member is in the form of a rod extending from the piston of said piston-cylinder assembly and movable axially toward and away from said drive unit, said cam means comprises a cam secured on an intermediate portion of said rod, and said latch having an intermediate contoured portion adapted to be engaged by said cam during initial axial movement of said rod toward said drive unit to release said latch.

10. The grinding machine defined in claim 9, including resilient means for holding said latch in latching position, said drive unit having means for swinging said latch away from its latching position against the action of said resilient means in response to retraction of said drive unit toward said predetermined position.

ll. The grinding machine defined in claim 9, including manually operable detent means for positively locking said latch in its latching position. 

1. A grinding machine comprising a grinding wheel, a drive unit having a belt extending to said grinding wheel to rotate the latter, a reversible power device having a lost-motion connection with said drive unit and operative when actuated in one direction to retract said drive unit away from said grinding wheel to a predetermined position tensioning said belt, latch means for holding said drive unit retracted in said predetermined position, and cam means carried by said power device and operative when said power device is actuated in the opposite direction to release said latch means and thereby untension said belt, said cam means effecting the release of said latch means within the limits of said lost-motion connection.
 2. A grinding machine comprising a grinding wheel, a drive unit movable toward and away from said grinding wheel and having a belt extending to said grinding wheel to rotate the latter, a reversible power device having a reciprocable member, a lost-motion connection between said reciprocable member and said drive unit for retracting said drive unit away from said grinding wheel to a predetermined position tensioning said belt when said reciprocable member is moved in one direction by said power device, said lost-motion connection permitting initial movement of said reciprocable member in the opposite direction without corresponding movement of said drive unit, latch means for holding said drive unit retracted in said predetermined position, and cam means carried by said reciprocable member and operative during said initial movement of said reciprocable member in said opposite directiOn to release said latch means.
 3. The grinding machine defined in claim 2, wherein said latch means comprises a pivoted latch having a hooked portion, said drive unit having a complementary member adapted to be engaged by the hooked portion of said latch to hold said drive unit retracted as aforesaid, said latch having a portion adapted to be engaged by said cam means during initial movement of said reciprocable member in said opposite direction to release said latch.
 4. The grinding machine defined in claim 3, including means mounting said complementary member on said drive unit in selected positions of adjustment in the direction of movement of said drive unit.
 5. The grinding machine defined in claim 3, including resilient means for holding said latch in its latching position.
 6. The grinding machine defined in claim 3, including releasable means for positively locking said latch in its latching position.
 7. The grinding machine defined in claim 2, wherein said latch means comprises a pivoted latch having a hooked end portion, said drive unit having a complementary member adapted to be engaged by the hooked portion of said latch to hold said drive unit retracted as aforesaid, said power device comprises a piston-cylinder assembly and said reciprocable member is in the form of a rod extending from the piston of said piston-cylinder assembly and movable axially toward and away from said drive unit, said cam means comprises a cam secured on an intermediate portion of said rod, and said latch having an intermediate contoured portion adapted to be engaged by said cam during initial axial movement of said rod toward said drive unit to release said latch.
 8. The grinding machine defined in claim 7, including means mounting said complementary member on said drive unit in selected positions of adjustment in the direction of movement of said drive unit.
 9. The grinding machine defined in claim 8, wherein said mounting means includes threadedly engaged members, said complementary member being formed on one of said threadedly engaged members, and said lost-motion connection being provided between said rod and said one of said threadedly engaged members.
 10. The grinding machine defined in claim 9, including resilient means for holding said latch in latching position, said drive unit having means for swinging said latch away from its latching position against the action of said resilient means in response to retraction of said drive unit toward said predetermined position.
 11. The grinding machine defined in claim 9, including manually operable detent means for positively locking said latch in its latching position. 